Inorganic nutrient input effects and severity of disturbance in zooplankton community structure

A microcosm experiment was conducted to test the effects and severity of inorganic nutrients inputs on a natural zooplankton community. A control and three nutrient inputs consisting of a singular pulse, continuous and pulse-continuous were applied to replicate diffuse inputs. Zooplankton community composition was analyzed, as well as the variable Z₂ (the score of the second principal dimension of a Correspondence Analysis) was used as a measurement of severity of the disturbance and was compared to six environmental situations with regular zooplankton community structure established in a previous study. Results showed notable differences in the final conditions of the pulse treatments, where decreased zooplankton biomass and presence of adults with eggs and nauplii suggested impaired reproduction and growth. The small-scale increases in Z₂ scores in the continuous treatments indicated a gradual, higher severity of disturbance over a longer period. The “cyclopoid situation” of the initial and final composition of the zooplankton assemblage suggested an initial external influence in a continuous state. This study highlights the effects of continuous inorganic nutrient inputs on plankton group dynamics and brings into focus the possible influence of subterranean waters as a diffuse nutrient source in confined Mediterranean coastal lagoons.